I have a 97 Dakota. I can drive it for about 15-20 miles and the truck shifts fine. Then it will downshift out of overdrive when you let off the gas. It will downshift sometimes at 55 mph. Then it will not shift back into overdrive no matter what you do. It has the 42re transmission. I have changed the fluid and filter (mopar +4) and it did not help. Also it will not idle properly. You can crank it up and keep your foot on the gas it runs fine, let off, the truck cuts off. Going down the road and let your foot off the gas to slow down and it will cut off also. You have to keep your foot on the ags at all times to keep it running. If you idle and let off extremly slowit may stay running. What can i do to fix these things. Are these things related.I dont have the money to take it to the shop, so please any help you can give me! I cando mechanic work. You have to when you have no money! Please help!

 

TPS or Crank Pos Sensor.
As for no overdrive, your pump might have gone. Or your temp solinoid might have gone, because if your not at operating temperature it will not allow you to shift into od.
Is there any codes being thrown?

 

try cleaning the idle air valve, its located on the back of the throttlebody up against the firewall and is held in with 2 torx screws that was what caused my truck to die when i let my foot off the gas, and it hasnt been a problem since so give it a try it cost nothing and it should be brassy in color, if its black than it could be the problem